Cataracts are the foremost cause of blindness in the world and currently can be treated only by surgical removal. Surgery, although easily available and safely performed in the U.S., is not easily available nor safely performed in many undeveloped regions in the world like Asia, Africa, the Middle East and South America. Hence we are studying ways to treat cataracts non-surgically, and a new device promises to help us find out what happens to the human lens that may cause cataracts, which will then help us find a cure for cataracts.One theory on the cause of cataracts is that some factors such as sunlight or lack of protective anti-oxidant vitamins may cause the proteins inside the lens to aggregate to form opaque high molecular weight "aggregates". Recently, a device has been created to determine molecular interactions, including lens crystalline interactions that occur in the nucleus of the lens, called Dynamic Light Scattering Device (DLS). Using the new DLS device on animal models of cataract, we have found evidence of this aggregation of proteins as a cataract appears.Preliminary studies have shown its potential in the detection of the earliest changes occurring in cataract, at the stage where anticataract treatment would theoretically be most effective in reversing, delaying or preventing cataracts. A new miniaturized version of this device has been developed by NASA using lower energy lasers and offered for further development and clinical testing at the NEI. We mounted the DLS device successfully on the Keratoscope, which had a 3-D aiming system to enhance repeatability. We recently conducted a pilot study on normal human volunteers (Phase 1) to evaluate the usefulness and reproducibility of this instrument for quantitating lens changes, and found good reproducibility. We also determined that the most useful parameter to use is mean particle size derived from particle size distribution. We now move into Phase 2 of this project to conduct a study on changes on the lens due to aging (age related changes), as well as on the three representative types of cataracts (nuclear, cortical and PSC). These data will help characterize molecular changes in the human lens associated with normal aging as well as those associated with cataract formation. With this information, we hope to better understand the underlying causes of cataracts and, in the future, develop medications to delay or prevent cataract formation.